1. Field of the Invention
The present invention generally relates to a lubricating system for use in a horizontal-type engine or a vertical-type engine including a crankcase and a cylinder block and, more specifically, to an improved oil seal and drain structure in such a lubricating system.
2. Description of the Related Art
Prior art type engines include a horizontal-type in which a crankshaft is disposed horizontally, and a vertical-type in which a crankshaft is disposed vertically. In the conventional engines, the crankcase and the cylinder block are different for each of the types, because of different conditions of the arrangement of a discharge passage for a blow-by gas produced in the crankcase and a return passage for oil separated from the blow-by gas and returned to the crankcase.
The different construction of the crankcase and the cylinder block in each of the types is inconvenient for providing a mass-produced engine, resulting in higher cost.
U.S. Pat. No. 5,937,836, the disclosure of which is expressly incorporated herein in its entirety, provides a solution to the above referenced problem, and presents an engine that is adapted for both horizontally and vertically-oriented crankshafts. The lubrication system of the ""836 patent has been found to work quite well in engines having either horizontally or vertically-oriented crankshafts. However, with the structure of the ""836 patent, there is presented a potential problem that, depending upon the engine displacement size and the configuration of the second bearing boss, there may be an excessive amount of oil communicated from the crankcase into the breather chamber when the crankshaft is vertically-oriented. While the breather chamber includes means to filter the oil out of the blow-by gas, the quantity of oil may be so great as to overwhelm the filtering means and therefore cause too much oil to be conveyed with the blow-by gas into the air cleaner of the engine intake system, leading to engine performance issues.
Accordingly, there exists a need in the art for an improved lubrication system for an engine having a vertically oriented crankshaft wherein the engine is otherwise generally adapted for use with either a horizontal or vertical crankshaft. There further exists a need in the art for such an engine that is adapted to limit or reduce the amount of oil that is conveyed with the blow-by gas into the breather chamber.
The present invention has been accomplished with such circumstance in view, and it is an object of the present invention to provide a lubricating system for a vertically-oriented crankshaft wherein discharge of the blow-by gas, the separation of oil from the blow-by gas, and the return of oil separated from the blow-by gas to the crankcase can be reliably performed. The present invention is therefore directed toward an improved lubrication system for an engine having a vertically oriented crankshaft wherein the engine is otherwise generally adapted for use with either a horizontal or vertical crankshaft. The present invention is further directed toward such an engine that is adapted to limit or reduce the amount of oil that is conveyed with the blow-by gas into the breather chamber.
In accordance with the present invention, a lubricating and breather system in an engine having a crankcase and a cylinder block adapted for use in either a horizontal-type or vertical-type engine is provided. The engine includes a crankshaft having first and second journal portions. The crankcase has first and second bearing bosses supporting the first and second journal portions of the crankshaft. The second bearing boss lies above the first bearing boss when the engine is of the vertical-type.
In further accordance with the present invention, the lubricating and breather system includes an annular chamber in the second bearing boss for receiving splashed oil produced in the crankcase. A breather chamber, which is in one side of the cylinder block, communicates with the annular chamber to separate blow-by gas and oil. For communication of oil to the crankcase, the breather chamber has a first return bore located at a portion thereof which is a lowermost portion when the engine is a horizontal-type and a second return bore located at a portion thereof which is a lowermost portion when the engine is a vertical-type.
In further accordance with the present invention, a breather tube is coupled to an intake system of the engine and connected to a portion of the breather chamber. The breather tube is located above the first return bore when the engine is a horizontal-type and above the second return bore when the engine is a vertical-type.
In further accordance with the present invention, a cap is secured over the second bearing boss and cooperates with the second bearing boss to define the annular chamber. The cap has a plurality of ribs formed thereon that serve to reduce the amount of oil that is communicated from the annular chamber to the breather chamber. The ribs include a plurality of radially directed ribs and an annular rib.
In further accordance with the present invention, the second bearing boss includes an oil feed hole through which oil and blow-by gases flow from the crankcase to the annular chamber. A plurality of oil return holes, through which oil is returned from the annular chamber to the crankcase, are formed in the second bearing boss. The oil return holes have a smaller diameter than that of the oil feed hole. The second bearing boss further includes a plurality of oil sumps, each of the oil sumps being associated with one of the oil return holes and being adapted to retain an amount of oil therein.